actually it wouldn't do anything as you have to be registered to send a private message anyway. If the spam bot registers then they will be able to view your profile. The spambots get the list of users from the member list which is public info for all registered members.

Yeah, you have to be a member to send a private message and you can only send to 10 people at a time. We've gotten two of these spammers so far, which sucks. Since we've moved to a much more popular forum software system, this is one of the drawbacks...a lot more resources focused on spamming it. I'm not sure what's the best way to handle it. I could make it so that you need to do one of those number verification things each time you log in, but then that makes it a pain for other users. I wish I could set it up to require verification for each message sent, but I don't see that as an option.